The present invention relates generally to compressed mode operation in a mobile communication system, and more particularly, to methods of controlling timing of uplink transmission by a plurality of mobile terminals operating in compressed mode.
A known problem with WCDMA phones is excessive power consumption that results in undesirable current drain and short battery life. When engaged in normal voice communications, a WCDMA phone transmits and receives continuously. This continuous operation is one of the primary reasons for the undesirable current drain in WCDMA phones. Another reason for current drain is the presence of a duplexer in the transmit path that increases path loss.
U.S. patent application Ser. No. 11/614,488 describes a method of reducing power consumption in a WCDMA phone by allowing the mobile terminals to switch to a compressed mode of operation. In the compressed mode, the mobile terminals transmit intermittently with a desired duty factor rather than continuously and increase their transmit power during the “on” periods to maintain the same data rate. Problems may arise with compressed mode operation if a significant number of mobile terminals operate in a compressed mode at the same time. Because the mobile terminals normally increase their transmit power in compressed mode, they will interfere with other users if too many mobile terminals transmit at the same time in the compressed mode. Further, too many mobile terminals switching their transmitters on and off at the same time may result in undesirably large swings in the uplink load.